1. Field of the Invention
The present invention relates to a connector block for electric power feed to injectors (fuel injection valves) in an internal combustion engine for use in an automobile or the like, and more particularly to the connector block of a type in which fuel passages are integrally incorporated.
2. Description of the Related Art
Conventionally, there has been known an internal combustion engine in which fuel is supplied to a plurality of cylinders by means of respective electromagnetic injectors. In this case, a connecting operation of an electric wiring to the individual injectors has been annoying and the structure has been complicated. In order to eliminate such drawbacks, there has been proposed a connector block which has connector parts for electrical connection to the injectors integrally made of synthetic resin material in a unit block. Japanese Publication No. JP-A-6-10789 of an examined patent application discloses one example of such structures. This type of the connector block has a fuel passage which is also formed integrally so as to distribute fuel to the respective injectors.
However, it has been pointed out that in such a connector block as the fuel passage is also incorporated inside the block, molding errors are likely to occur at a portion to be the fuel passage. This is because the connector block will be long-sized in a direction of arrangement of the cylinders, and accordingly, a core for molding the fuel passage will become also long-sized. Moreover, some of the fuel passages are of a closed structure at its rear end, and in this case, the core must be necessarily of a cantilever structure. For this reason, when the core receives an injecting pressure at the molding, the core tends to cause a positional displacement. Under such a situation, it has been likely to happen that the fuel passage is molded out of an accurate position.
When such the positional displacement as described above has happened, a uniform thickness of a wall of the fuel passage in a circumferential direction cannot be attained, but a deviation of thickness will be formed in a part of the wall. This means that cooling speed cannot be constant in a circumferential direction when a molded product is cooled after taken out from the molds. Accordingly, rate of shrinkage will be uneven in a circumferential direction of the fuel passage, and the whole block will be deflected. Further, in many cases busbars as the electric wiring are also incorporated in the injectors. In such cases too, a structural deviation of the wall thickness tends to happen, and voids or sink marks are likely to be created.
As a countermeasure to solve such problems, it has been considered that the core is retained by means of support pins projected from the metal molds and abutted against the core. However, in this case, there will be created through holes communicating with the fuel passage in the block, and the through holes must be closed by some sealing means. This leads to new problems such as addition of working steps and security of the seal, and cannot be said as an effective measure.
The invention has been developed in order to solve the above described problems, and it is an object of the invention to provide a connector block for injectors which has a high grade of molding quality.
In order to attain the above described object, according to a first aspect of the invention, there is provided is a connector block for injectors which comprises a block body made of synthetic resin material and provided with a plurality of injector mounting parts which are arranged at a determined interval in a longitudinal direction, a wiring part for electric power feed to the injectors, and a fuel supply part formed in the block body in a longitudinal direction and adapted to distribute fuel to the injectors, characterized in that the block body is molded in a state where the fuel supply part which has been molded separately therefrom is embedded inside.
According to a second aspect of the invention, there is provided a connector block for injectors as defined in the first aspect of the invention, characterized in that the fuel supply part is in a tubular shape including a fuel passage inside, and is further provided, at an outer face thereof, with positioning means to position the block body with respect to metal molds for molding the block body.
According to a third aspect of the invention, there is provided a connector block for injectors as defined in the first aspect of the invention, characterized in that the fuel supply part is made of metal.
According to the first aspect of the invention, the connector block is molded by placing the fuel supply part which has been previously prepared into the metal molds, and thereafter, filling a resin in the molds. Even though the molded product (the connector block) taken out from the metal molds should be deviated in the wall thickness, the fuel supply part placed inside will serve as the core member when the molded product is cooled and can effectively resist against the deflection.
The idea of providing the positioning means for the fuel supply part on the metal molds is by no means denied by the first aspect of the invention. Even in case where such positioning means are provided on the metal molds, traces of the positioning means extracted after the molding will only allow an outer face of the fuel supply part to be exposed, but will not create such through holes reaching an interior of the fuel supply part as in the conventional case, thus eliminating a necessity of sealing.
According to the second aspect of the inventions the fuel supply part is placed in position in the metal molds by the aid of the positioning means, and therefore the positional displacement will not occur even with the injecting pressure of the resin. As described, the fuel supply part will be molded at the accurate position, and the molding precision and molding quality will be enhanced.
Further, the fuel supply part made of metal as in the third aspect of the invention can surely resist against the injecting pressure of the resin, and the deflection will be more reliably prevented.